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New Mexico State University

New Mexico State University

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Locoweed Guide Helps Ranchers Identify Poisonous Plants

LAS CRUCES -- Bean and pea plants have some rangeland relatives that cause problems for New Mexico's ranchers. About 75 different species of white-, purple- and blue-flowered locoweeds grow in the state, fewer than 20 of which are poisonous to livestock. To help tell them apart, New Mexico State University researchers have compiled a field guide to common locoweeds.


"We've written this book for all sorts of people: ranchers, farmers and the interested amateur naturalist who likes to get out and notice wildflowers," said Kelly Allred, plant scientist with NMSU's Agricultural Experiment Station. "It's especially geared for people in agriculture, those who have rangeland or livestock concerns."

Locoweeds and closely related milkvetches are in the same family as our familiar peas, beans and mesquite, Allred said.

Poisonous locoweed species are among the most toxic plants to livestock, causing millions of dollars in losses every year in the West. The plants get their name from the dramatic symptoms they produce in cattle. Poisoned or "loco" animals may stagger aimlessly, stumble into objects or even charge at people. In large doses, locoweed causes abortion and death in cattle.

Locoweed tempts livestock as one of the first green plants on the range in the spring and one of the last to fade in late fall or winter. Once livestock begin grazing it, they seem to become addicted, grazing it at every opportunity.

To prevent poisoning, ranchers can keep rangeland in good condition, provide supplemental feed, remove cattle from infested pastures and chemically treat locoweed.

The field guide has photos, drawings, descriptions, maps and even a computer program to help users identify nontoxic and toxic locoweeds and prevent livestock poisoning.

"We have a section on management that will help ranchers deal with these kinds of plants, how they would control them and what kinds of grazing strategies they would use," Allred said. "Most of the book is about identification, though, so that if they find one of these plants out in the field, they can pick the flowers or the pods and look through the book."

The book germinated from NMSU graduate students' research. While earning his master's degree in range science, Bill Fox traveled throughout New Mexico, photographing and collecting locoweed. His research contributed to the maps that show the location of various species.

"Sometimes master's theses are hidden away in the laboratory and nobody gets to read them, so we wanted to put together this book so people could have the information," Allred said.

A second student, Eric Roalson, completed a computer program to help identify locoweed while working on his master's degree in range science at NMSU.

"This field guide has practical value for New Mexico ranchers," said David Graham, Union County agent with NMSU's Cooperative Extension Service. More information about ongoing locoweed research will be presented during a field day this fall at the Clayton Livestock Research Center, he said.

To purchase a $15 copy of "A Guide to the Common Locoweeds and Milkvetches of New Mexico," call the NMSU bulletin office at (505) 646-3228. County Extension offices statewide can also provide more information about locoweed.